1. Field of the Invention
The present invention relates generally to infectious diseases and, more particularly, to the prevention, diagnosis and treatment of infections caused by gram negative bacteria.
Bacterial sepsis and related septic shock are frequently lethal conditions caused by infections which can result from certain types of surgery, abdominal trauma and immune suppression related to cancer, transplantation therapy or other disease states. It is estimated that over 700,000 patients become susceptible to septic shock-causing bacterial infections each year in the United States alone. Of these, 160,000 actually develop septic shock, resulting in 50,000 deaths annually.
Gram negative bacterial infections comprise the most serious infectious disease problem seen in modern hospitals. Two decades ago, most sepsis contracted in hospitals was attributable to more acute gram positive bacterial pathogens such as Staphylococcus and Streptococcus. By contrast, the recent incidence of infection due to gram negative bacteria, such as Escherichia coli and Pseudomonas aeruginosa, has increased.
Gram negative bacteria now account for some 200,000 cases of hospital-acquired infections yearly in the United States, with an overall mortality rate in the range of 20% to 60%. The majority of these hospital-acquired infections are due to such gram negative bacilli as E. coli (most common pathogen isolated from patients with gram negative sepsis), followed in frequency by Klebsiella pneumoniae and P. aeruginosa.
Gram negative sepsis is a disease syndrome resulting from the systemic invasion of gram negative rods and subsequent endotoxemia. The severity of the disease ranges from a transient, self-limiting episode of bacteremia to a fulminant, life-threatening illness often complicated by organ failure and shock. The disease is often the result of invasion from a localized infection site, or may result from trauma, wounds, ulcerations or gastrointestinal obstructions. The symptoms of gram negative sepsis include fever, chills, pulmonary failure and septic shock (severe hypotension).
Gram negative infections are particularly common among patients receiving anti-cancer chemotherapy and immunosuppressive treatment. Infections in such immuno-compromised hosts characteristically exhibit resistance to many antibiotics, or develop resistance over the long course of the infection, making conventional treatment difficult. The ever increasing use of cytotoxic and immunosuppressive therapy and the natural selection for drug resistant bacteria by the extensive use of antibiotics have contributed to gram negative bacteria evolving into pathogens of major clinical significance.
Fortunately, more than a decade ago, investigators in the United States and Germany demonstrated that gram negative endotoxins of many different bacterial genera have a "common core structure." In other words, while many infectious gram negative organisms contain individual capsule and surface polysaccharides, there is a core lipopolysaccharide (LPS) structure that is widely shared among the diverse gram negative bacterial genera and their endotoxins.
This core structure contains material identified as "lipid A" that is felt to be responsible for all of the biologic properties of "endotoxin," including pyrogenicity, activation of the complement and clotting systems, hypotension and death in experimental animals. This core or LPS structure is therefore significant for at least two reasons; its association with endotoxicity and its conservation in gram negative bacterial genera.
Because antibiotic treatment remains largely suboptimal against gram negative sepsis, particularly that associated with P. aeruginosa bacterial infection, (antibiotics are only effective in treating the bacteria and not in reducing the effects of microbial endotoxins) attention has increasingly focused on immunologic methods to prevent and control such infections. Immunotherapy involves the administration of immunoglobulins (antibodies or active fragments thereof) to bolster the host's native defenses against the toxic effects of the bacteria, for example, by enhancing opsonization and phagocytosis of the infecting bacterial cells, or by neutralization of the biological effects of LPS. Antibodies, or active fragments thereof, that bind with the core structure or lipid A, i.e., LPS, could have a broad reactivity with a number of gram negative endotoxins.
Antibodies directed against epitopes or antigenic determinants on the O-specific side chains of smooth gram negative bacteria have limited utility for use in immunotherapy. This is because they are effective against only those strains of bacteria having complementary or cross-reactive antigenic determinants. Such strain-specific antibodies are of only limited utility. While the core oligosaccharide and lipid A of all strains are thought to share antigenic determinants, the few previous attempts to produce and utilize monoclonal antibodies reactive with these regions in Pseudomonas have been largely unsuccessful.
Immunoglobulins that bind most of the clinically significant gram negative pathogens are essential to the success of immunotherapy. P. aeruginosa organisms, which account for 5% to 15% of bloodstream infections, have at least 16 different serotypes (O-antigenic types). Klebsiella organisms have more than 80 capsular types, and E. coli organisms, which are far more common, have more than 130 serotypes.
Patients with bacteremia often do not have a confirmed specific diagnosis as to the type of bacterial infection until bacteriologic results are available, which may take several days. Therapy often must be started based on an empirical diagnosis in order to prevent a patient's condition from rapidly deteriorating during the critical first 24 to 48 hours of illness.
There therefore exists a longstanding need for the production of monoclonal antibodies (MoAb), or active fragments thereof, reactive with an epitope or antigenic determinant present on all important pathogenic strains of gram negative bacteria, thus permitting effective diagnosis, prophylaxis, control of bacterial infection and neutralization of associated endotoxemia attributable to gram negative bacterial genera. It would also be beneficial to have available MoAbs which are cross-reactive with gram positive bacteria useful in the diagnosis, treatment and prevention of bacterial infections generally.
2. Description of the Relevant Literature
Bacterial infections have received widespread treatment in the scientific and patent literature. Much of this treatment has focused on sepsis due to gram negative bacterial endotoxin. The following is a list of relevant articles and published applications and a brief description of each:
EP O No. 101 039 A2, published Feb. 22, 1984, discloses a monoclonal antibody to Pseudomonas aeruginosa and methods for its use in diagnosis and therapy;
WO No. 84/04458, published Nov. 22, 1984, discloses MoAbs reactive with endotoxin core;
WO No. 85/01659, published Apr. 25, 1985, discloses MoAbs against endotoxin of gram negative bacteria;
EP O No. 163 493, published Apr. 12, 1985, discloses human MoAbs against gram negative bacteria and specific for serotypic determinants of lipopolysaccharide useful for treating or preventing P. aeruginosa infection;
Feingold et al., Arch. Int. Med. (1965) 116:326-28, describe the use of polyclonal antisera derived from human patients recovering from gram negative infection to effectively treat gram negative sepsis in a human patient;
Abe et al., Jpn. J. Exp. Med. (1975) 45:355-59, describe the use of polyclonal antisera produced in response to immunization of mice with P. aeruginosa endotoxin;
Apicella et al., Infect. Immun. (1981) 34:751-56, report the analysis of lipopolysaccharide from Neisseria gonorrhorae and N. meningitidis using monoclonal antibodies;
Zeigler et al., N. Eng. J. Med. (1982) 307:1225-30, report the results of a double-blind trial wherein gram negative bacteremic human patients were treated with human antiserum prepared by vaccinating healthy donors with heat-killed E. coli J5 mutant;
Hancock et al., Infect. Immun. (1982) 37:166-71, describe MoAbs specific for Pseudomonas aeruginosa outer membrane antigens;
Hiernaux et al., Eur. J. Immunology (1982) 12:797-803 describe MoAbs specific for E. coli 0113 lipopolysaccharide (LPS);
Machie et al., J. Immunol. (1982) 129:829-32, describe MoAbs which bind gram negative bacteria of different genera;
Young L. S., Clin. Res. (1982) 30:518A, describe MoAbs prepared using S. minnesota RS-95 LPS as the immunogen;
Pollack et al., J. Clin, Invest. (1983) 72:1874-81, report enhanced survival of P. aeruginosa septicemia associated with high levels of circulating antibody to E. coli endotoxin core;
Sawada et al., J. Infect. Dis. (1984) 150:570-76, report protection in mice against infection with P. aeruginosa by passive transfer of MoAbs to lipopolysaccharides and outer membrane proteins;
Three relevant abstracts were included in Abstracts of the 24th Interscience Conference on Antimicrobial Agents and Chemotherapy (1984) 106: Black and Cannon, "Monoclonal antibody to common pathogenic neisseria antigen (H8Ag) protects against meningococcemia (ME) in mice"; Williams et al., "Panreactive monoclonal antibody (MCA) to Porin Protein F of Pseudomonas aeruginosa (PA): Passive immunotherapy in mice"; and Kim, et al., "Studies of the protective mechanism of monoclonal antibodies against E. coli";
Mutharia et al., Infect. Immun. (Sept. 1984) 45:631-36, describe MoAbs cross-reactive with gram negative bacteria of different genera believed to bind lipid A and not reactive with gram positive bacteria;
Nelles and Niswander, Infect. Immun. (Dec. 1984) 46:677-81, describe two mouse monoclonal antibodies reactive with lipopolysaccharide derived from the J5 mutant of E. coli 0111:B4 which binds lipopolysaccharide from both smooth and rough phenotype, gram negative bacteria;
Young et al., Clin. Res. (1984) 32:522A, describe a MoAb directed against the "core" of glycolipid of enterobacterial endotoxin;
Young L. S., Principles and Practice of Infectious Disease (1985) John Wiley and Sons, N.Y., N.Y., pp. 452-75, provides an overview of gram negative sepsis;
Sadoff et al., Antibiot. Chemother. (1985) 36:134-46, describe the characterization of mouse monoclonal antibodies directed against P. aeruginosa lipopolysaccharides;
Teng et al., Proc. Nat. Acad. Sci. U.S.A. (March 1985) 82:1790-94, report the protection of mice against gram negative bacteremia and endotoxemia with human monoclonal IgM antibodies. The MoAbs showed no significant protection from gram positive bacterial infection;
Giglliotti and Shenep, J. Infect. Dis. (June 985) 151:1005-11, describe MoAbs that bind LPS from E. coli rough mutant J5 but do not bind intact smooth strains of E. coli 0111:B4 or K1:07;
Peters et al., Infect. Immun. (Nov. 1985) 50:459-66, describe MoAbs to enterobacterial common antigen and E. coli lipopolysaccharide outer core and demonstrate a shared antigenic determinant believed to be at least in part 4-linked .alpha.-N-acetylglucosamine;
Dunn et al., Surgery (August 1985) 98:283-90, report the production of a strain specific binding MoAb using E. coli smooth strain 0111:B4 as the immunogen and the production of a gram negative bacteria cross-reactive MoAb using E. coli rough mutant J5 as the immunogen. These MoAbs were not reactive with gram positive bacteria;
Dunn et al., Arch. Surg. (Jan 1986) 121:58-62, report on the immunotherapy of gram negative sepsis employing a single murine monoclonal IgG antibody, demonstrating reactivity with a variety of gram negative organisms, promotion of phagocytosis and providing protection during experimental gram negative sepsis. Also, the MoAb showed no reactivity with gram positive bacteria tested;
Miner et al., Infect. Immune. (April 1986) 52:56-62, describe the characterization of murine MoAbs to E. coli J5.